However the energetics of pentapedal walking indicated that it was less energy efficient than walking on four legs, says Dawson.
"This was always a puzzle," he says.
While previous literature suggested kangaroos used their tail as a "strut to hold the body in place while they move the back legs forward," Dawson suspected something else was happening.
"It appeared to me they were using the tail for propulsion when walking," he says.
To test this hypothesis, Dawson and colleagues trained one male and four female red kangaroos (Macropus rufus) to walk over a force-measuring platform that monitored the energy used by different parts of the kangaroo as it walked.
The researchers found that kangaroos walk by using the tail to lift both hind legs and the body's centre of gravity forward, while the forelimbs were used as struts and didn't provide any of the propulsion.
The tests showed there was far more propulsion energy provided by the tail than scientists had thought.
The kangaroo's tail provides as much propulsive energy as one of the hind legs, between a quarter and a third of the full propulsion needed to move the animal forward, they found.